From U.S. Pat. No. 6,588,443 B2 is already known a method for controlling a compressed air unit, and in particular for discharging condensate from a multi-stage compressor unit, whereby the condensate which is formed in a cooler of each respective pressure stage is discharged via a drain pipe provided downstream said pressure stage to that end.
A disadvantage of such a method according to U.S. Pat. No. 6,588,443 B2 is that many valves are required and that a device for applying such a method is voluminous, as several valves and connections are present. Another disadvantage of such a method is that it cannot be used to perform other functions than to discharge condensate.
From EP 0,391,250 A2 is known a device which can be used to discharge a condensate until a set level is reached, as soon as another pre-set maximum level of condensate has been reached in a collector.
A disadvantage of this configuration is that no other measuring signals are taken into account and that such a configuration is only suitable for discharging the condensate coming from only one collector to an open reservoir, and in that it cannot be used to perform other functions.
U.S. Pat. No. 6,196,253 B1 describes a drain valve to immediately discharge condensate when it is present at the inlet of said drain valve. The disadvantage of such a valve gear, however, is that it can only be used to discharge condensate from a single reservoir to an open reservoir. Another disadvantage is the lack of a large volume, which implies that many work cycles are required to discharge large volumes of condensate.